U.S. patent application number 12/206089 was filed with the patent office on 2008-12-25 for magnetic tape write once overwrite protection.
Invention is credited to KIRBY GRANT DAHMAN, Paul Merrill Greco, Glen Alan Jaquette, Steven Michael Wallace.
Application Number | 20080316634 12/206089 |
Document ID | / |
Family ID | 36970570 |
Filed Date | 2008-12-25 |
United States Patent
Application |
20080316634 |
Kind Code |
A1 |
DAHMAN; KIRBY GRANT ; et
al. |
December 25, 2008 |
MAGNETIC TAPE WRITE ONCE OVERWRITE PROTECTION
Abstract
A magnetic tape cartridge, a recording system, and a magnetic
tape drive are configured to, for example, guard against tampering
with a write once overwrite protection pointer which allows a
rewritable magnetic tape to be treated as write once. In one
embodiment, the magnetic tape cartridge comprises a magnetic tape
and a cartridge memory. The magnetic tape is configured to provide
at least one overwrite protection pointer, the overwrite protection
pointer identifying data to be protected from being overwritten;
and the cartridge memory is configured to provide the at least one
overwrite protection pointer, the overwrite protection pointer
identifying magnetic tape data to be protected from being
overwritten.
Inventors: |
DAHMAN; KIRBY GRANT;
(Seattle, WA) ; Greco; Paul Merrill; (Tucson,
AZ) ; Jaquette; Glen Alan; (Tucson, AZ) ;
Wallace; Steven Michael; (Tucson, AZ) |
Correspondence
Address: |
JOHN H. HOLCOMBE;IBM CORPORATION, IP LAW DEPT.
8987 E. TANQUE VERDE RD., #309-374
TUCSON
AZ
85749
US
|
Family ID: |
36970570 |
Appl. No.: |
12/206089 |
Filed: |
September 8, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11076643 |
Mar 10, 2005 |
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12206089 |
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Current U.S.
Class: |
360/60 ;
G9B/15.006; G9B/15.009; G9B/23.051; G9B/23.077; G9B/23.087 |
Current CPC
Class: |
G11B 23/288 20130101;
G11B 23/042 20130101; G11B 23/107 20130101; G11B 15/07
20130101 |
Class at
Publication: |
360/60 ;
G9B/15.006 |
International
Class: |
G11B 15/04 20060101
G11B015/04 |
Claims
1-8. (canceled)
9. A magnetic tape cartridge comprising: a magnetic tape configured
to provide a plurality of updateable overwrite protection pointers
at each of two separate areas of said magnetic tape, said overwrite
protection pointers identifying a location of said magnetic tape
that identifies data to be protected from being overwritten; and
said overwrite protection pointers configured to be updated in a
sequence.
10. The magnetic tape cartridge of claim 9, wherein said magnetic
tape updateable overwrite protection pointers are configured to be
time-stamped when updated, to identify the current valid overwrite
protection pointer.
11. The magnetic tape cartridge of claim 9, wherein said magnetic
tape updateable overwrite protection pointers are configured to
duplicate the current valid overwrite protection pointer to
identify the current valid overwrite protection pointer.
12. The magnetic tape cartridge of claim 9, wherein said magnetic
tape updateable overwrite protection pointers are configured to
identify the end of data that is to be protected from being
overwritten, prior to end of file constructs.
13. The magnetic tape cartridge of claim 9, wherein said magnetic
tape is configured to provide said at least one overwrite
protection pointer as at least a part of "beginning of tape"
information.
14. The magnetic tape cartridge of claim 9, wherein said magnetic
tape is configured to provide said at least one overwrite
protection pointer as at least a part of "data set information
table".
15. A magnetic tape cartridge comprising: a cartridge memory
configured to provide a plurality of updateable overwrite
protection pointers, said overwrite protection pointers identifying
a location of said magnetic tape that identifies magnetic tape data
to be protected from being overwritten; and said overwrite
protection pointers configured to be updated in a sequence.
16. The magnetic tape cartridge of claim 15, wherein said cartridge
memory updateable overwrite protection pointers are configured to
be time-stamped when updated, to identify the current valid
overwrite protection pointer.
17. The magnetic tape cartridge of claim 15, wherein said cartridge
memory updateable overwrite protection pointers are configured to
duplicate the current valid overwrite protection pointer to
identify the current valid overwrite protection pointer.
18. The magnetic tape cartridge of claim 15, wherein said cartridge
memory updateable overwrite protection pointers are configured to
identify the end of data that is to be protected from being
overwritten, prior to end of file constructs.
19-26. (canceled)
27. A recording system for magnetic tape, comprising: logic
configured to record a plurality of updateable overwrite protection
pointers at each of two separate areas on said magnetic tape, said
overwrite protection pointers identifying a location of said
magnetic tape that identifies data to be protected from being
overwritten; and said logic configured to update said overwrite
protection pointers in a sequence.
28. The recording system of claim 27, wherein: said logic
configured to record at least one overwrite protection pointer on
said magnetic tape is configured to time-stamp said magnetic tape
updateable overwrite protection pointers when updated, to identify
the current valid overwrite protection pointer.
29. The recording system of claim 27, wherein: said logic
configured to record at least one overwrite protection pointer on
said magnetic tape is configured to duplicate the current valid
said magnetic tape updateable overwrite protection pointer, to
identify the current valid overwrite protection pointer.
30. The recording system of claim 27, wherein: said logic
configured to record at least one overwrite protection pointer on
said magnetic tape is configured to provide said overwrite
protection pointer, identifying the end of data that is to be
protected from being overwritten, prior to end of file
constructs.
31. The recording system of claim 27, wherein said logic configured
to record at least one overwrite protection pointer on said
magnetic tape is configured to provide said at least one overwrite
protection pointer as at least a part of "beginning of tape"
information.
32. The recording system of claim 27, wherein said logic configured
to record at least one overwrite protection pointer on said
magnetic tape is configured to provide said at least one overwrite
protection pointer as at least a part of "data set information
table".
33. A recording system for magnetic tape, said magnetic tape
mounted with respect to a magnetic tape cartridge having a
cartridge memory, comprising: logic configured to provide a
plurality of updateable overwrite protection pointers to said
cartridge memory, said overwrite protection pointers identifying a
location of said magnetic tape that identifies magnetic tape data
to be protected from being overwritten; and said logic configured
to update said overwrite protection pointers in a sequence.
34. The recording system of claim 33, wherein: said logic
configured to provide said at least one overwrite protection
pointer to said cartridge memory, is configured to time-stamp said
cartridge memory updateable overwrite protection pointers when
updated, to identify the current valid overwrite protection
pointer.
35. The recording system of claim 33, wherein: said logic
configured to provide said at least one overwrite protection
pointer to said cartridge memory, is configured to duplicate the
current valid said cartridge memory updateable overwrite protection
pointer, to identify the current valid overwrite protection
pointer.
36. The recording system of claim 33, wherein: said logic
configured to provide at least one overwrite protection pointer to
said cartridge memory, is configured to provide said overwrite
protection pointers, identifying the end of data that is to be
protected from being overwritten, prior to end of file
constructs.
37-44. (canceled)
45. A recording system for magnetic tape, said magnetic tape
mounted with respect to a magnetic tape cartridge, comprising:
logic configured to compare a plurality of overwrite protection
pointers of said magnetic tape cartridge, at least one said
overwrite protection pointer read from said magnetic tape; and
logic configured to determine from said comparison the validity of
said overwrite protection pointers.
46-47. (canceled)
48. A magnetic tape drive configured to read and write information
with respect to a magnetic tape, said magnetic tape mounted with
respect to a magnetic tape cartridge, comprising: at least one
motor configured to move said magnetic tape longitudinally; at
least one read/write head configured to read from and to write to
said magnetic tape while said magnetic tape is moved longitudinally
by said at least one motor; at least one recording channel
configured to operate said at least one read/write head to read
from and to write to said magnetic tape; a memory interface
configured to communicate with respect to said cartridge memory;
and at least one control system configured to operate said at least
one recording channel to read a plurality of overwrite protection
pointers recorded on said magnetic tape at each of two separate
areas of said magnetic tape, said overwrite protection pointers
identifying a location of said magnetic tape that identifies data
to be protected from being overwritten; and configured to compare
said read overwrite protection pointers, and determine from said
comparison the validity of said overwrite protection pointers.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the utilization of rewritable
magnetic tape as write once media, for example, known as
write-once-read-many ("WORM") media.
BACKGROUND OF THE INVENTION
[0002] Magnetic tape is typically a rewritable recording media, but
may be rendered as write once media by limiting overwrite of the
media. For example, copending and coassigned U.S. Pat. No.
6,339,810, Basham et al., discusses treating data storage media as
WORM by automatically advancing a write append limiter as data is
written, and preventing changes to data occurring before the write
append limiter.
SUMMARY OF THE INVENTION
[0003] In one embodiment, a magnetic tape cartridge is configured
to, for example, guard against tampering with a write once
overwrite protection pointer. The magnetic tape cartridge comprises
a magnetic tape and a cartridge memory. The magnetic tape is
configured to provide at least one overwrite protection pointer,
the overwrite protection pointer identifying data to be protected
from being overwritten; and the cartridge memory is configured to
provide the at least one overwrite protection pointer, the
overwrite protection pointer identifying magnetic tape data to be
protected from being overwritten.
[0004] In a further embodiment, a recording system for magnetic
tape, the magnetic tape mounted with respect to a magnetic tape
cartridge having a cartridge memory, comprises logic configured to
record at least one overwrite protection pointer on the magnetic
tape, the overwrite protection pointer identifying data to be
protected from being overwritten; and logic configured to provide
the overwrite protection pointer to the cartridge memory, the
overwrite protection pointer identifying magnetic tape data to be
protected from being overwritten.
[0005] Still further, a magnetic tape drive is configured to read
and write information with respect to a magnetic tape mounted with
respect to a magnetic tape cartridge having a cartridge memory. The
magnetic tape drive comprises at least one motor configured to move
the magnetic tape longitudinally; at least one read/write head
configured to read from and to write to the magnetic tape while the
magnetic tape is moved longitudinally by the motor(s); at least one
recording channel configured to operate the read/write head(s) to
read from and to write to the magnetic tape; a memory interface
configured to communicate with respect to the cartridge memory; and
at least one control system configured to operate the at least one
recording channel to record at least one overwrite protection
pointer on the magnetic tape, the overwrite protection pointer
identifying data to be protected from being overwritten; and
configured to operate the memory interface to provide the at least
one overwrite protection pointer to the cartridge memory, the
overwrite protection pointer identifying magnetic tape data to be
protected from being overwritten.
[0006] In a further embodiment, the magnetic tape overwrite
protection pointer and the cartridge memory overwrite protection
pointer, comprises a plurality of updateable overwrite protection
pointers, the overwrite protection pointers configured to be
updated in a sequence.
[0007] In an alternative embodiment, a plurality of updateable
magnetic tape overwrite protection pointers may be updated in a
sequence (with or without overwrite protection pointers in the
cartridge memory); and in a further alternative embodiment, a
plurality of updateable cartridge memory overwrite protection
pointers may be updated in a sequence (with or without magnetic
tape overwrite protection pointers).
[0008] In further embodiments, the magnetic tape and/or the
cartridge memory updateable overwrite protection pointers are
configured to be time-stamped when updated, to identify the current
valid overwrite protection pointer.
[0009] In still further embodiments, the magnetic tape and/or the
cartridge memory updateable overwrite protection pointers are
configured to duplicate the current valid overwrite protection
pointer to identify the current valid overwrite protection
pointer.
[0010] In still further embodiments, the magnetic tape at least one
overwrite protection pointer and/or the cartridge memory at least
one overwrite protection pointer are configured to identify the end
of data that is to be protected from being overwritten, prior to
end of file constructs.
[0011] In still further embodiments, the magnetic tape is
configured to provide at least one overwrite protection pointer as
at least a part of "beginning of tape" information.
[0012] In still further embodiments, the magnetic tape is
configured to provide at least one overwrite protection pointer as
at least a part of "data set information table".
[0013] In another embodiment, the magnetic tape is configured to
provide a copy of the at least one cartridge memory overwrite
protection pointer to a "housekeeping data set" of the magnetic
tape.
[0014] For a fuller understanding of the present invention,
reference should be made to the following detailed description
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an isometric view of a magnetic tape cartridge
with a magnetic tape and a cartridge memory shown in phantom;
[0016] FIG. 2 is a block diagrammatic representation of a magnetic
tape drive for handling the magnetic tape cartridge of FIG. 1;
[0017] FIG. 3 is a diagrammatic representation of information
provided on a magnetic tape, comprising beginning of tape
information and a data set;
[0018] FIG. 4 is a diagrammatic representation of information
provided in a cartridge memory, including WORM information;
[0019] FIG. 5 is a diagrammatic representation of information
related to an overwrite protection pointer; and
[0020] FIG. 6 is a diagrammatic representation of information
related to a data file provided on a magnetic tape.
DETAILED DESCRIPTION OF THE INVENTION
[0021] This invention is described in preferred embodiments in the
following description with reference to the Figures, in which like
numbers represent the same or similar elements. While this
invention is described in terms of the best mode for achieving this
invention's objectives, it will be appreciated by those skilled in
the art that variations may be accomplished in view of these
teachings without deviating from the spirit or scope of the
invention.
[0022] Referring to FIG. 1, an example of a magnetic tape cartridge
10 in which the present invention may be employed is illustrated
which comprises a rewritable magnetic tape 11 wound on a hub 12 of
reel 13, and a cartridge memory 14. One example of a magnetic tape
cartridge comprises a cartridge based on LTO (Linear Tape Open)
technology. The cartridge memory 14, for example, comprises a
transponder having a contactless interface, which is retained in
the cartridge 10, for example, by being encapsulated by the
cartridge when it is assembled, as is understood by those of skill
in the art. The illustrated magnetic tape cartridge is a single
reel cartridge. Magnetic tape cartridges may also comprise dual
reel cartridges in which the tape is fed between reels of the
cartridge.
[0023] Referring to FIG. 2, a magnetic tape drive 15 is
illustrated. One example of a magnetic tape drive in which the
present invention may be employed is the IBM 3580 Ultrium magnetic
tape drive based on LTO technology, with microcode, etc., to
perform desired operations with respect to the magnetic tape
cartridge 10. In the instant example, the magnetic tape 11 is wound
on a reel 13 in the cartridge 10, and, when loaded in the magnetic
tape drive 15, is fed between the cartridge reel and a take up reel
16 in the magnetic tape drive. Alternatively, both reels of a dual
reel cartridge are driven to feed the magnetic tape between the
reels.
[0024] The magnetic tape drive comprises a memory interface 17 for
reading information from, and writing information to, the cartridge
memory 14 of the magnetic tape cartridge 10, for example, in a
contactless manner. A read/write system is provided for reading and
writing information to the magnetic tape, and, for example, may
comprise a read/write and servo head system 18 with a servo system
for moving the head laterally of the magnetic tape 11, a read/write
servo control 19, and a drive motor system 20 which moves the
magnetic tape 11 between the cartridge reel 13 and the take up reel
16 and across the read/write and servo head system 18. The
read/write and servo control 19 controls the operation of the drive
motor system 20 to move the magnetic tape 11 across the read/write
and servo head system 18 at a desired velocity, and, in one
example, determines the location of the read/write and servo head
system with respect to the magnetic tape 11. In one example, the
read/write and servo head system 18 and read/write and servo
control 19 employ servo signals on the magnetic tape 11 to
determine the location of the read/write and servo head system, and
in another example, the read/write and servo control 19 employs at
least one of the reels, such as by means of a tachometer, to
determine the location of the read/write and servo head system with
respect to the magnetic tape 11. The read/write and servo head
system 18 and read/write and servo control 19 may comprise hardware
elements and may comprise any suitable form of logic, including a
processor operated by software, or microcode, or firmware, or may
comprise hardware logic, or a combination.
[0025] A control system 24 communicates with the memory interface
17, and communicates with the read/write system, e.g., at
read/write and servo control 19. The control system 24 may comprise
any suitable form of logic, including a processor operated by
software, or microcode, or firmware, or may comprise hardware
logic, or a combination.
[0026] The illustrated and alternative embodiments of magnetic tape
drives are known to those of skill in the art, including those
which employ dual reel cartridges.
[0027] The control system 24 typically communicates with one or
more host systems 25, and operates the magnetic tape drive 15 in
accordance with commands originating at a host. Alternatively, the
magnetic tape drive 15 may form part of a subsystem, such as a
library, and may also receive and respond to commands from the
subsystem.
[0028] As illustrated, the magnetic tape drive 15 provides
information to the cartridge memory 14 of the magnetic tape
cartridge 10, and provides information to the magnetic tape 11 of
the magnetic tape cartridge 10.
[0029] Referring to FIG. 3, a magnetic tape 11 may be organized in
many ways. Typically, a magnetic tape is arranged with parallel
tracks, and may also be arranged with several parallel wraps of
groups of parallel tracks. In one example, the magnetic tape is
moved longitudinally in a first direction while the head system
reads and/or writes data with respect to one wrap, and is reversed
to be moved in the opposite direction and the head system is
shifted to another wrap.
[0030] In FIG. 3, the information is shown laid out as a single
wrap for the purpose of illustration. An area 40 at or near the
front end of the magnetic tape 11 is called the "beginning of tape"
(BOT) as is known to those of skill in the art. In a single reel
magnetic tape cartridge, this is the area of one or more wraps near
the front end of the magnetic tape (leader block) that is loaded
into the take up reel 16 of the magnetic tape drive 15 as depicted
in FIG. 2. In a dual reel magnetic tape cartridge, an area of the
magnetic tape near the center, about halfway between one reel and
the other, is typically designated the BOT, and may comprise one or
more wraps. Such a dual reel magnetic tape cartridge is also
referred to as a midpoint load tape.
[0031] Referring to FIG. 3, in one embodiment, the magnetic tape
cartridge is configured to provide, among the information of the
BOT, such as initialization information 42 and housekeeping
information 44, one or more write once overwrite protection
pointers 45 which identify data to be protected from being
overwritten, and thereby allow a rewritable magnetic tape to be
treated as write once.
[0032] Also, a magnetic tape typically records data in the form of
"data sets" 46 or similar arrangements of data. In one example,
each complete data set is accompanied by a "data set information
table" 47 which provides information about the data set 46. In one
embodiment, each data set information table 47 provides at least
one write once overwrite protection pointer 49 which identifies
data to be protected from being overwritten, and thereby allows a
rewritable magnetic tape to be treated as write once. The write
once overwrite protection pointers 49 may comprise an addition to
or an alternative to the write once overwrite protection pointers
45 at the BOT.
[0033] Referring to FIG. 4, an example of the content of the
cartridge memory 14 of the magnetic tape cartridge 10 of FIGS. 1
and 2 is illustrated. One example of a cartridge memory 14 and its
content is described in Standard ECMA-319, June 2001, "Data
Interchange on 12, 7 mm 384-Track Magnetic Tape
Cartridges--Ultrium--1 Format", Annex D--LTO Cartridge Memory, pp.
95-115. As one example, the cartridge memory 14 is arranged in
areas of various sizes with information organized into "pages". The
cartridge memory 14 may be similar to the memory and transponder
used in "smart cards" as are known to those of skill in the art.
Those of skill in the art may envision additional types of
cartridge memories.
[0034] Referring to FIG. 4, in one embodiment, information 50 about
the magnetic tape cartridge is provided, in addition to WORM
information 52. The WORM information may, for example, indicate a
level of WORM protection, any read protection limiting access to
the data to be read, etc., and at least one write once overwrite
protection pointer 55 which identifies data to be protected from
being overwritten, and which thereby allows a rewritable magnetic
tape to be treated as write once.
[0035] FIG. 5 illustrates an embodiment of a write once overwrite
protection pointer 60 (OPP) which may comprise a magnetic tape
overwrite protection pointer 45 at the BOT of FIG. 3, may comprise
a magnetic tape overwrite protection pointer 49 in a DSIT of FIG.
3, or may comprise a cartridge memory overwrite protection pointer
55 of FIG. 4.
[0036] Referring to FIG. 5, an overwrite protection pointer 60
identifies a location 62. As an example, the identified location
may comprise the wrap and the offset from a starting point, such as
the number of servo timing or longitudinal distance marks from a
starting point. Still alternatively, the location may be identified
by means of a count of the number 64 of filemarks recorded to the
magnetic tape from the BOT to the identified location.
Alternatively, or additionally, the location may be identified by
means of a count of the number 66 of the records recorded to the
magnetic tape from the BOT to the identified location. The location
identified by an overwrite protection pointer is the location
before which is protected from being overwritten.
[0037] If a plurality of overwrite protection pointers 60 are
provided, a timestamp 68 may be provided to identify the current
valid overwrite protection pointer. The timestamp may or may not be
a direct part of the overwrite protection pointer, but is
associated with the pointer.
[0038] Referring to FIGS. 1, 2, 3, 4 and 5, in accordance with an
embodiment of the present invention, a magnetic tape cartridge 10,
a recording system 24, 19, 18, and a magnetic tape drive 15 are
configured to, for example, guard against tampering with a write
once overwrite protection pointer which allows a rewritable
magnetic tape to be treated as write once. The magnetic tape 11 is
configured to provide at least one overwrite protection pointer 45,
49, the overwrite protection pointer identifying data to be
protected from being overwritten; and the cartridge memory 14 is
configured to provide the at least one overwrite protection pointer
55, the overwrite protection pointer identifying magnetic tape data
to be protected from being overwritten. In these embodiments, the
presence of the overwrite protection pointer in both the magnetic
tape 11 and the cartridge memory 14 guards against tampering.
[0039] Alternatively, or additionally, the presence of the
overwrite protection pointers 45, 49 at two separate areas of the
magnetic tape 11 guards against tampering.
[0040] Referring to FIGS. 3 and 4, in another embodiment of the
present invention, the magnetic tape overwrite protection pointer
45 and/or 49, and/or the cartridge memory overwrite protection
pointer 55, comprises a plurality of updateable overwrite
protection pointers, the overwrite protection pointers configured
to be updated in a sequence. In one example, the sequence is in a
circular order, e.g. OPP#0, OPP#1, OPP#2, OPP#3, OPP#0, . . . In
one example, the sequentially updated overwrite protection pointers
preserve the lifecycle of a cartridge memory.
[0041] In an alternative embodiment, a plurality of updateable
magnetic tape overwrite protection pointers 45 and/or 49 may be
updated in a sequence (with or without overwrite protection
pointers in the cartridge memory); and in a further alternative
embodiment, a plurality of updateable cartridge memory overwrite
protection pointers 55 may be updated in a sequence (with or
without magnetic tape overwrite protection pointers).
[0042] Referring to FIG. 5, in further embodiments, the magnetic
tape and/or the cartridge memory updateable overwrite protection
pointers 60 are configured to be time-stamped 68 when updated, to
identify the current valid overwrite protection pointer, as
discussed above. The time stamp may be an indication of the number
of times that the magnetic tape cartridge has been loaded to a
magnetic tape drive, or may be a clock time of a subsystem in which
the magnetic tape drive is located, for example, a library.
[0043] Alternatively, the overwrite protection pointers 60 may be
arranged in a sequence, for example, of an ever increasing location
value, in that no previously protected area is later "unprotected".
As the result, the newest OPP is always an increased value, and the
highest value is by nature the latest. In this sense, the location
value of the OPP may be considered the equivalent of
"timestamp".
[0044] Alternatively, referring to FIG. 5, the count of the number
64 of filemarks recorded to the magnetic tape from the BOT to the
identified location, and/or the count of the number 66 of the
records recorded to the magnetic tape from the BOT to the
identified location may comprise timestamps. Those of skill in the
art can envision additional time stamp embodiments.
[0045] In still further embodiments, additionally or alternatively,
the magnetic tape and/or the cartridge memory updateable overwrite
protection pointers are configured to duplicate the current valid
overwrite protection pointer to identify the current valid
overwrite protection pointer. Referring to FIGS. 3 and 4, the
current valid overwrite protection pointer may comprise OPP#1, and
be designated as the current valid overwrite protection pointer by
having the pointer duplicated as OPP#2. The duplication may be
accomplished upon receipt of an unload request by the magnetic tape
drive 15 of FIG. 2. As an example, if OPP#1 is written after a
string of user data is written, and then an unload request is
received, the contents of OPP#1 is copied to OPP#2.
[0046] When a new cartridge is loaded, the magnetic tape drive 15
recording system 24, 19, 18 of FIG. 2 determines the latest
overwrite protection pointer by means of the timestamps as
discussed above. It should have the latest timestamp or be tied
with the latest timestamp. The second copy is verified as well. The
second copy is then overwritten when the first OPP update occurs on
the new load. In the above example, the first update would be to
OPP#2, because it is the second copy of the previous final OPP.
[0047] If a duplicate OPP is not found which matches the OPP with
the latest timestamp, then another set of the OPP's is consulted to
provide OPP integrity. For example, referring to FIGS. 3 and 4, if
OPP#2 does not agree with OPP#1 of the OPP's 45 in the BOT, then
OPP#1 and OPP#2 of the OPP's 55 of the cartridge memory are
consulted. In another example, if OPP#2 does not agree with OPP#1
of the OPP's 45 in the BOT, then OPP#1 and OPP#2 of the OPP's 49 of
the DSIT at the expected end of data (EOD) are consulted.
[0048] Integrity of the overwrite protection pointer may be
provided by arranging the overwrite protection pointers in a
sequence, for example, of an ever increasing value, as discussed
above. Thus, the highest location value OPP is by nature the
latest.
[0049] Additional integrity checks may be made to insure that an
OPP is always greater or equal to any logically preceding OPP's,
and existing OPP's, for example, in the DSIT's, are less than or
equal to "current" OPP's from the cartridge memory. As such, the
OPP integrity is maintained in the absence of, or in addition to,
timestamps.
[0050] Thus, in a further embodiment of the present invention, the
overwrite protection pointers are read and compared to check for
validity and, if validity is not insured, i.e. the cartridge memory
and tape OPP's do not match, there is no duplicate OPP or the last
OPP does not have the latest timestamp or does not have the
greatest value, then the cartridge will be treated as lacking OPP
integrity. For example, the tape could be treated as read only, or
treated as a "tampered" tape and disallowed from all read and/or
write processing. Alternatively, data could be appended only at the
logical end of tape. The selection of these or other options may be
arbitrary or based on information found by the various OPP
methods.
[0051] Referring to FIGS. 2, 3, 4 and 5, control 24, in one
embodiment, is configured to operate the recording channel 18, 19
to read at least one OPP from magnetic tape 11, and to operate the
memory interface 17 to read at least one OPP from cartridge memory
14. In another embodiment, a plurality of overwrite protection
pointers are read from the magnetic tape 11. The logic then
determines from the read overwrite protection pointers, e.g. by
comparing at least two of the read OPP's, the validity of the
OPP's.
[0052] Another method of assuring integrity of the overwrite
protection pointers is to interlock the OPP's with "good status"
which is returned to the application which wrote the record or File
Mark which caused the OPP to be advanced.
[0053] In an additional embodiment of the present invention, the
sequence of updating the overwrite protection pointers may be to
update the pointers 49 of the DSIT of the last data set written
when an unload command is received by the magnetic tape drive,
called the end of data (EOD) data set, the pointers 55 of the
cartridge memory are then updated, and, lastly, the contents of the
cartridge memory WORM information is copied to the housekeeping
section of the BOT, thereby providing the updated pointers 45.
[0054] In a further embodiment of the present invention, the
overwrite protection pointers may identify locations that are at
the end of completed data that has been written, in order to allow
an application to overwrite incomplete constructs and change or
update labels, such as to update or invalidate information.
[0055] In another embodiment of the present invention, the
overwrite protection pointers may identify locations that are at
the end of data, prior to the end of file or similar constructs, to
allow an application to append data to what had been an end of data
or end of file.
[0056] Referring to FIG. 6, the information is shown laid out as a
single wrap of magnetic tape 11 for the purpose of illustration.
Typical constructs include a label 70 at a beginning of a
partition, and header 71 at the beginning, for example, of a file,
followed by user data 73. A trailer 75, such as at the end of a
user file, may indicate the end of a file and, for example,
comprise a filemark 76, a first end of file indicator 77, a second
end of file indicator 78, and another filemark 79.
[0057] In the example of FIG. 6, the overwrite protection pointer
60 of FIG. 5 thus is configured to identify the location 80 of FIG.
6, at the end of the user data 73 and prior to the end of file
constructs of trailer 75. Similarly, the OPP does not identify a
header 71, but rather is moved with the data. Those of skill in the
art will envision similar locations in similar constructs.
[0058] Thus, the application can go back and forth and change
candidate constructs and the OPP will identify the data after it is
completely and finally written by the application. For example, the
DSIT having the updated OPP (or OPP's) will be the end of data
(EOD) data set.
[0059] Those of skill in the art will understand that changes may
be made with respect to the number or content of the OPP's and to
their locations. Further, those of skill in the art will understand
that differing specific component arrangements may be employed than
those illustrated herein.
[0060] While the preferred embodiments of the present invention
have been illustrated in detail, it should be apparent that
modifications and adaptations to those embodiments may occur to one
skilled in the art without departing from the scope of the present
invention as set forth in the following claims.
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